Patent Application
20110177679
1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device provided with a nitride semiconductor layer formed on a substrate having a low-dislocation region and a high-dislocation region; and specifically, relates to a method for manufacturing a semiconductor device that can improve the surface flatness of the nitride semiconductor layer.
2. Background Art
When a nitride semiconductor layer is formed on a substrate having a low-dislocation region and a high-dislocation region, abnormal growth generated on the high-dislocation region may be transmitted to the low-dislocation region causing the degradation of the flatness of the nitride semiconductor layer. To solve such a problem, ,a method for preventing abnormal growth on the high-dislocation region by forming an insulating film so as to cover the high-dislocation region has been proposed (for example, refer to Japanese Patent Application Laid-Open No. 2004-221480).
Conventionally, since an insulating film has been formed so as to cover a high-dislocation region, the insulating film has inevitably widened. Therefore, during the growth of the nitride semiconductor layer, materials are diffused from the insulating film, and the nitride semiconductor layer is thickened in the vicinity of the insulating film. As a result, there have been problems wherein the surface flatness of the nitride semiconductor layer is degraded, and the yield of elements is lowered.
In view of the above-described problems, an object of the present invention is to provide a method for manufacturing a semiconductor device that can improve the surface flatness of the nitride semiconductor layer.
According to the present invention, a method for manufacturing a semiconductor device comprises: preparing a substrate having a low-dislocation region and a high-dislocation region having a higher dislocation density than a dislocation density of the low-dislocation region; forming an insulating film on the low-dislocation region so as to surround the high-dislocation region but not to cover the high-dislocation region; and forming a nitride-based semiconductor layer on the substrate after forming the insulating film.
The present invention makes it possible to improve the surface flatness of the nitride semiconductor layer.
Other and further objects, features and advantages of the invention will appear more fully from the following description.
A method for manufacturing a semiconductor device according to an embodiment of the present invention will be described referring to the drawings.
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In addition, light-emitting elements (not shown) are periodically formed on the nitride semiconductor layer 18 formed on the low-dislocation region 10. Specifically, the nitride semiconductor layer 18 is constituted of an n-type GaN layer of a thickness of 1 μm, an n-type A0.07Ga0.93N of a thickness of 1 μm, an n-type GaN layer of a thickness of 100 nm, an active layer, an p-type Al0.2Ga0.8N layer of a thickness of 20 nm, a p-type GaN layer of a thickness of 10 nm, a p-type Al0.07Ga0.93N of a thickness of 400 nm, and a p-type GaN layer of a thickness of 100 nm sequentially laminated from the GaN substrate 14. The active layer is a multiple quantum well wherein 3 cycles of In0.02Ga0.9N layers each having a thickness of 3.5 nm and In0.02Ga0.98N layers each having a thickness of 7 nm are laminated.
The effects of the present embodiment will be described comparing with a comparative example.
Also, since the high-dislocation region 12 is not covered by the insulating film 16, the width w of the insulating film 16 can be reduced. Therefore, the thickening of the nitride semiconductor layer 18 in the vicinity of the insulating film 16 due to the diffusion of materials can be prevented. As a result, the surface flatness of the nitride semiconductor layer 18 can be improved, and the yield of the semiconductor devices can be elevated. Specifically, in order to improve the surface flatness, the width w of the insulating film 16 is made to be not more than 30 μm. However, in order to prevent the transmitting of abnormal growth, the width w of the insulating film 16 must be not less than 1 μm.
Also, the thickness of the insulating film 16 is preferably 500 to 5000 Å. This is because if the insulating film 16 is thinner than 500 Å, the nitride semiconductor layer 18 is laterally grown on the insulating film 16 to cover the insulating film 16; and if the insulating film 16 is thicker than 5000 Å, stress due to the formation of the insulating film 16 is significantly enlarged to warp the substrate. It is further preferable to make the thickness of the insulating film 16 be 1000 to 2000 Å.
Also, the insulating film 16 is preferably composed of SiO2 or SiN. Thereby, the nitride semiconductor layer 18 is little grown on the insulating film 16. SiO2 or SiN is stable even at a high temperature of around 1000° C.
In the present embodiment, although the high-dislocation region 12 and the insulating film 16 are stripe-shaped, if the insulating film 16 has the shape to surround the high-dislocation region 12, the high-dislocation region 12 and the insulating film 16 may have the shape other than stripe-shape.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
The entire disclosure of a Japanese Patent Application No. 2010-010056, filed on Jan. 20, 2010 including specification, claims, drawings and summary, on which the Convention priority of the present application is based, are incorporated herein by reference in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-010056 | Jan 2010 | JP | national |
